This invention relates generally to an apparatus and a method for reclaiming waste oil, and more particularly relates to reclaiming waste oil from a sludge, i.e. a highly viscous material containing a relatively large amount of contaminants and particulate solids.
In this specification, the term xe2x80x9cwaste oilxe2x80x9d encompasses any suitable oil, for example mineral oils which have been used as motor oil, or some other lubricating oil, or as hydraulic oil or in some other application. It is anticipated that these oils will have been derived from mineral oil, but they could be, for example, animal or vegetable oil, such as fish oil or oil discarded by restaurants, etc. The mineral oil could be plain crude oil. In use, such lubricating oils are usually changed periodically. The drained and recovered waste oil typically contain substantial amounts of contaminants, which may include dirt, metallic particles (including heavy metals, such and molybdenum, chromium, cadmium, vanadium, copper, etc.), oxides and salts, gasoline and gasoline additives (such as tetraethyl lead) as well detergents and performance additives. It may also be contaminated with water. Large quantities of such waste oil are produced in industrialized countries, and my earlier inventions were directed to methods and apparatus for recovering waste oil, so that it would be suitable for various uses. The contaminants in waste oil usually make it unsuitable for most uses. The term xe2x80x9cwaste oilxe2x80x9d further includes an oil-based sludge such as that produced in the apparatus of my earlier invention described in application Ser. No. 246,834.
My earlier inventions provided an apparatus in which the lighter hydrocarbons of the waste oil were volatized and then condensed. Also, whilst the exact mechanism within the apparatus was not fully understood, it is believed that some cracking or splitting of the hydrocarbons from longer to shorter chain molecules occur. Indeed, it is even possible that the contaminants present acted as a catalyst. It was discovered that starting with contaminated, waste lubricating Oil, approximately 90% of this could be converted into a lighter oil, suitable for use as a diesel fuel.
My earlier inventions are disclosed in detail in U.S. Pat. No. 5,271,808, which discloses a basic refiner (secondary treater), and U.S. Pat. No. 5,286,349, which discloses a more advanced process and apparatus identified here as a preprocessor (primary treater). The contents of these two U.S. patents are hereby incorporated by reference.
The basic process of the refiner provided distillation with some cracking, carried out at substantially atmospheric pressure. This enabled the waste oil to be recovered as a diesel grade fuel oil, free of solid impurities and the like. This process left solids and other impurities concentrated as a sludge, which presented disposal problems. The later invention, the preprocessor, provided a process in which, when the solids and other impurities had built up to a certain level, further supply of waste oil is cut off, and the temperature raised to drive off all remaining organic and volatile components. This left a friable, cake-like material which has been classified as a xe2x80x9ctoxic non-leachatexe2x80x9d, which means that it can be disposed of readily in most jurisdictions.
However, a problem with the oil or diesel grade fuel recovered from either of my earlier inventions, is that it tended to be unstable. Practically, it is believed that the oil contained a number of free radicals and/or olefins. Consequently, over a period of time, these free radicals or olefins would combine, forming heavy oils and tars. Since the intention was to recover the oil as a diesel-grade fuel, this presented considerable problems. Such tar and heavy components tend to deposit in fuel injection systems and the like, clogging the systems and preventing proper operation.
Accordingly, it is desirable to provide an improvement or modification of my existing processes, which results in a recovered oil product which is stable, and which can be stored for a significant period of time, typically of the order of 30 days, without any serious or significant degradation or changes in characteristics, more particularly, without deposition of any tars or heavy hydrocarbons.
In accordance with the present invention, there is provided a method of reclaiming a useful oil product from a waste oil, the method comprising the steps of:
(1) heating the waste oil to vaporize oil therefrom;
(2) injecting hydrogen gas into the vaporized oil, to cause saturation of at least some of olefins and free radicals present in the vaporized oil; and
(3) recovering the waste oil as a useful oil product.
The waste oil is vaporized at substantially atmospheric pressure, as this then eliminates the requirement to provide complex or costly pressure vessels or the like. Thus, steps (1) and (2) could be carried out at a pressure equivalent to up to 30 inches of water above atmospheric pressure.
More preferably, the temperature is sufficient to cause at least partial cracking of the oil. Advantageously, the recovered oil is condensed and recovered as a liquid.
Advantageously, the waste oil is heated in an evaporation chamber and oil is continuously supplied to the evaporation chamber, and the level of waste oil in the evaporation chamber is monitored, to maintain said level within desired limits.
In a preferred embodiment, the vaporized oil is passed through a connection duct from the evaporation chamber to a condensation and, for step (2) hydrogen is injected into the oil vapour in at least one of the evaporation chamber and the connection duct.
Advantageously, the hydrogen passes through a duct extending through liquid waste oil into the evaporation chamber, to preheat the hydrogen to the temperature within the evaporation chamber.
In accordance with my earlier preprocessor invention, the method can include an additional step (5): after a period of time, terminating supply of waste oil to the evaporation chamber and continuing to heat the evaporation chamber and waste oil therein in a bake mode to a substantially higher temperature, to vaporize substantially all residual waste oil in the evaporation chamber, to leave a solid residue within the evaporation chamber.
In accordance with another aspect of the present invention, there is provided a method of reclaiming a useful oil product from a waste oil the method being carried out substantially continuously and at substantially atmospheric pressure, and the method comprising the steps of:
(1) continuously supplying waste oil to an evaporation chamber;
(2) heating the waste oil in the evaporation chamber to generate oil vapours therefrom;
(3) injecting hydrogen gas into the oil vapours to cause saturation of at least some of olefins and free radicals present in the oil vapours; and
(4) recovering and condensing the hydrogenated oil vapours as a useful oil product;
wherein all of the oil supplied in step (1) and all of the oil vapours generated in step (2) are recovered in step (4)
The method can be carried out in an apparatus for reclaiming a useful oil product from a waste oil, the apparatus comprising: an evaporation chamber, including an inlet for the waste oil, and an outlet for vaporized oil, as a useful oil product; a heating means for heating the evaporation chamber to vaporize oil from the waste oil; a means for injecting hydrogen into waste oil vapour; and a means for recovering the vaporized oil.
Preferably, the apparatus includes a condensation means and a connection duct connecting the outlet of the evaporation chamber to the condensation means. The means for injecting hydrogen advantageously comprises a conduit opening into at least one of an upper portion of the evaporation chamber and the connection duct. A part of the conduit can extend through a lower portion of the evaporation chamber, whereby hydrogen in the conduit is heated by the waste oil to the temperature within the evaporation chamber.
For continuous operation and in accordance with my earlier inventions, the evaporation chamber can include an inlet for waste oil, and the apparatus then includes a pump means for supplying waste oil to the evaporation chamber; and level control means for monitoring the level of waste oil within the evaporation chamber, the level control means being connected to the pump means and actuating the pump means to maintain waste oil level within desired limits. For operation as a preprocessor, the heating means is preferably connected to the level control means and, in a normal mode of operation, is disabled if the oil level goes outside the desired limits, and the apparatus further includes means for disabling the level control means and terminating the supply of waste oil, to enable continued operation of the heating means in a bake mode, in which the evaporation chamber is heated to an elevated temperature to vaporize remaining hydrocarbons.